The structure activity relationships of unsubstituted, n-butyl, propionic acid, and butan-3-one analogs of 3-hydroxyphthalimidine, indazolone, homophthalimide, phthalazine-1, 4-dione, 1,8-naphthalimide, glutarimide, o-benzoicsulfimide, indan-1, 3-dione, 3-imino-1-oxoisoindoline, phthalimidine, 1,2-benzoisothiazoline-1, 1-dioxide, indan-1-one, succinimide, maleimide, D,L-2,3-dimethylsuccinimide will be synthesized and tested for their ability to lower serum cholesterol and triglyceride levels in rats and mice in normal and hyperlipidemic states. Acute toxicity (LD50 values) will be determined for potent antihyperlipidemic agents of this series. Both in vivo and in vitro studies will be conducted to determine if imide analogues suppress the regulatory enzymes of cholesterol, fatty acid in triglyceride synthesis, e.g. HMG CoA reductase, acetyl CoA synthetase, ATP dependent-citrate lyase, citrate exchange from mitochondria, acetyl CoA carboxylase, fatty acid synthetase, phosphatidate phosphohydrase, acyl transferase and lipoprotein lipase activities of the liver. The effects of imides on plasma lipoproteins will also be examined.